Modern motor vehicles usually employ contoured or wrapped windshields. Windshield wiper systems, in order to effectively clean the outer surface of such windshields, typically comprise a carrier yoke system consisting of several parts for guiding a rubber wiper element. The carrier yoke system mostly includes a primary yoke onto which two secondary yokes, namely clawed yokes are swivellably mounted. In wiper blades having a short lateral length, the secondary yoke is mounted to the primary yoke via a plastic link with pivot pins laterally sticking out. In wiper blades of larger lateral length, the secondary yoke is mounted to the primary yoke via a metallic rivet pin. Concerning both solutions, there are advantages and disadvantages. When using a plastic link, the mostly metallic yokes are prevented from touching each other and thus disturbing noises are avoided. However, these embodiments with a plastic link do not always meet the requirement of stability and unadmissably large play cannot be avoided after an extended period of operation.
The stability of the riveted wiper blade is better, but the corrosional behavior does not meet all the requirements, for in these wiper blades the rivet head is formed by a tumbling riveting process so that a press-fit is produced by deforming the rivet shank immediately under the rivet head, and the articulated rivet and the primary yoke are connected with each other in a sufficiently firm way. However, during this tumbling riveting process sometimes the varnish of the yoke is damaged so that this point of corrosion is increased. Thus, however, the rivet connection is also damaged so that, after all, a non-rotatable connection between the articulated rivet and the primary yoke is no longer guaranteed. The consequence thereof is that again the apertures in the side walls of the primary yoke are worn out and thus the play in the articulation becomes so big that the wiping effort is no longer sufficient.
The above described system of interconnected yokes is typical in modern automotive windshield wiper element support structures designed to maintain a uniform pressure along the length of the blade. Such structures typically have multiple joints, in which the structure is designed to articuate, allowing blade conformance to the windshield shape through the entire wipe stroke. It is important to maintain the freedom of articulation in the structure or the windshield will have areas not wiped, thereby restricting the vehicle operator's vision.
Wiper arm assembles employing such articulated joints are particularly problematic when the vehicle is operated in a snowy or sub-freezing environment. Inevitably, frozen precipitation will accumulate in the area of the windshield wiper blade structures. Present technology of blade structure joints allow the precipitation to accumulate between the joints in a way that requires the articuation action to compress the ice in order to work. This solid mass cannot be compressed and therefore the articulation action ceases to exist as long as the solid is present. The windshield wiper performance is therefore greatly diminished until the solid precipitation is somehow removed through melting or clearing through external means.